Can't disolve edge and faces
A face is a polygon. A polygon is an array of vertices.

The way it is interpreted is:


Make a first triangular part with vertices 1, 2, 3
Then make another one with 2, 3, 4
Then 3, 4, 5
Etc.


This does not allow to have holes in it except if there is only 1 hole, or in some special cases for example if the holes are triangular themselves (at least, I think, this is surely a complex topology problem...).

So, my though is that you can dissolve only if there is a path of triangles "calculable" all along this polygon. And I don't think this is the case here due to the 3 square holes. Or if you dissolve, the polygon will cover/overlap the windows.